U.S. patent application number 14/785549 was filed with the patent office on 2016-03-17 for intelligent sea water cooling system.
The applicant listed for this patent is IMO Industries, Inc.. Invention is credited to Alistair Baird, Edwin Braun, Martin Hoffmann, Christian Hopf, Christian Martin, David McKinstry, Stefan Werner, Dan Yin.
Application Number | 20160076434 14/785549 |
Document ID | / |
Family ID | 51731764 |
Filed Date | 2016-03-17 |
United States Patent
Application |
20160076434 |
Kind Code |
A1 |
Yin; Dan ; et al. |
March 17, 2016 |
Intelligent Sea Water Cooling System
Abstract
An intelligent sea water cooling system including a first fluid
cooling loop coupled to a heat exchanger, a second fluid cooling
loop coupled to the heat exchanger and including a fluid pump for
circulating fluid through the second fluid cooling loop, and a
controller operatively connected to the fluid pump. The controller
may be configured to monitor an actual temperature in the first
fluid cooling loop and to adjust a speed of the fluid pump based on
the monitored temperature in order to achieve a desired temperature
in the first fluid cooling loop.
Inventors: |
Yin; Dan; (Waxhaw, NC)
; Werner; Stefan; (Allensbach, DE) ; McKinstry;
David; (Charlotte, NC) ; Braun; Edwin;
(Allensbach, DE) ; Martin; Christian; (Radolfzell,
DE) ; Hoffmann; Martin; (Moos, DE) ; Hopf;
Christian; (Mullhausen-Ehingen, DE) ; Baird;
Alistair; (Saunderstown, RI) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
IMO Industries, Inc. |
Hamilton |
NJ |
US |
|
|
Family ID: |
51731764 |
Appl. No.: |
14/785549 |
Filed: |
April 9, 2014 |
PCT Filed: |
April 9, 2014 |
PCT NO: |
PCT/US14/33422 |
371 Date: |
October 19, 2015 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61813822 |
Apr 19, 2013 |
|
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|
Current U.S.
Class: |
123/41.02 ;
165/296 |
Current CPC
Class: |
B63H 21/10 20130101;
F01P 3/207 20130101; F01P 2050/06 20130101; B63H 21/383 20130101;
F01P 7/164 20130101 |
International
Class: |
F01P 7/16 20060101
F01P007/16; B63H 21/10 20060101 B63H021/10; F01P 3/20 20060101
F01P003/20 |
Claims
1. A variable flowrate cooling system, comprising: a first fluid
cooling loop coupled to a first side of a heat exchanger; a second
fluid cooling loop coupled to a second side of the heat exchanger
and including a pump for circulating fluid through the second fluid
cooling loop; and a controller operatively connected to the pump,
wherein the controller is configured to monitor an actual
temperature in the first fluid cooling loop and to adjust a speed
of the pump based on the monitored temperature in order to achieve
a desired temperature in the first fluid cooling loop.
2. The variable flowrate cooling system of claim 1, further
comprising a temperature detector associated with the first fluid
cooling loop, the controller operatively coupled to the temperature
detector to receive signals representative of the temperature of
the first fluid.
3. The variable flowrate cooling system of claim 2, wherein the
temperature detector is positioned immediately upstream from a
thermal load.
4. The variable flowrate cooling system of claim 3, wherein the
thermal load is a diesel engine.
5. The variable flowrate cooling system of claim 1, wherein the
second fluid cooling loop comprises a once through seawater
loop.
6. The variable flowrate cooling system of claim 5, wherein the
first fluid cooling loop comprises a closed freshwater loop.
7. The variable flowrate cooling system of claim 1, wherein the
pump comprises first and second pumps, and the controller comprises
first and second controllers associated with the first and second
pumps, respectively, wherein the first and second controllers are
operatively coupled to communicate operational information there
between.
8. The variable flowrate cooling system of claim 1, wherein the
controller is configured to determine a system efficiency, based on
the speed of the pump and the detected temperature, and to command
operation of a second pump when two pump operation is determined to
be more efficient than one pump operation.
9. A method for providing variable sea water cooling flow to a heat
exchange element, the method comprising: circulating a first fluid
in a first cooling loop at a first flow rate, the first cooling
loop coupled to a first side of a heat exchanger; circulating a
second fluid in a second cooling loop at a second flow rate, the
second cooling loop coupled to a second side of the heat exchanger;
detecting a temperature of the first fluid; and adjusting the
second flow rate to maintain a temperature of the first fluid
within a predetermined temperature range.
10. The method of claim 9, wherein the temperature is detected
immediately upstream from a thermal load.
11. The method of claim 10, wherein the thermal load is a diesel
engine.
12. The method of claim 10, wherein the second fluid is seawater,
and the step of circulating the second fluid comprises operating a
pump at a variable speed to adjust the second flow rate.
13. The method of claim 12, wherein adjusting the flow rate is
performed using a controller associated with the pump.
14. The method of claim 13, wherein the pump comprises first and
second pumps, and the adjusting step is performed by first and
second controllers associated with the first and second pumps,
respectively, the method further comprising communicating
operational information between the first and second controllers,
the operational information relating to the first and second
pumps.
15. The variable flowrate cooling system of claim 1, wherein the
controller is configured to determine a system efficiency, based on
the speed of the pump and the detected temperature, and to command
operation of a second pump when two pump operation is determined to
be more efficient than one pump operation.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is related to and claims priority from U.S.
Provisional Patent Application No. 61/813,822, filed on Apr. 19,
2013, by Daniel Yin, et al., entitled: "Intelligent Sea Water
Cooling System", which is incorporated herein by reference in its
entirety.
FIELD OF THE DISCLOSURE
[0002] The disclosure is generally related to the field of sea
water cooling systems for seafaring vessels, and more particularly
to a system and method for controlling the temperature in a fresh
water cooling loop by regulating pump speed in a sea water cooling
loop thermally coupled thereto.
BACKGROUND OF THE DISCLOSURE
[0003] Large seafaring vessels are commonly powered by large
internal combustion engines that require continuous cooling under
various operating conditions, such as during high speed cruising,
low speed operation when approaching ports, and full speed
operation for avoiding bad weather, for example. Existing systems
for achieving such cooling typically include one or more pumps that
draw sea water into heat exchangers onboard a vessel. The heat
exchangers are used to cool a closed, fresh water cooling loop that
flows through and cools the engine(s) of the vessel and/or other
various loads onboard the vessel (e.g., air conditioning
systems).
[0004] A shortcoming that is associated with existing sea water
cooling systems such as the one described above is that they are
generally inefficient. Particularly, the pumps that are employed to
draw sea water into such systems are typically operated at a
constant speed regardless of the amount of sea water necessary to
achieve sufficient cooling of the associated engine. Thus, if an
engine does not require a great deal of cooling, such as when the
engine is idling or is operating at low speeds, or if the sea water
being drawn into a cooling system is very cold, the pumps of the
cooling system may provide more water than is necessary to achieve
sufficient cooling. In such cases, the cooling system will be
configured to divert an amount of the freshwater in the freshwater
loop directly to the discharge side of the heat exchangers, where
it mixes with the rest of the freshwater that flowed through, and
was cooled by, the heat exchangers. A desired temperature in the
freshwater loop is thereby achieved. However, the system does not
require the full cooling power provided by sea water pumps driven
at constant speed (hence the need to divert water in the fresh
water loop). A portion of the fuel expended in driving the pumps is
therefore unnecessary. Thus, there is a need for a more efficient
sea water pumping system for use in heat exchange systems servicing
the marine industry.
SUMMARY
[0005] In view of the foregoing, it would be advantageous to
provide an intelligent sea water cooling system and method that
provide improved efficiency and fuel savings relative to existing
sea water cooling systems and methods.
[0006] An exemplary system in accordance with the present
disclosure may include a first fluid cooling loop coupled to a heat
exchanger, a second fluid cooling loop coupled to the heat
exchanger and including a pump for circulating fluid through the
second fluid cooling loop, and a controller operatively connected
to the fluid pump. The controller may be configured to monitor an
actual temperature in the first fluid cooling loop and to adjust a
speed of the pump based on the monitored temperature in order to
achieve a desired temperature in the first fluid cooling loop.
[0007] A method is disclosed for providing variable sea water
cooling flow to a heat exchange element. The method comprises:
circulating a first fluid in a first cooling loop at a first flow
rate, the first cooling loop coupled to a first side of a heat
exchanger; circulating a second fluid in a second cooling loop at a
second flow rate, the second cooling loop coupled to a second side
of the heat exchanger; detecting a temperature of the first fluid;
and adjusting the second flow rate to maintain a temperature of the
first fluid within a predetermined temperature range.
BRIEF DESCRIPTION OF THE DRAWINGS
[0008] By way of example, specific embodiments of the disclosed
device will now be described, with reference to the accompanying
drawings, in which:
[0009] FIG. 1 is a schematic view illustrating an exemplary
intelligent sea water cooling system in accordance system.
[0010] FIG. 2 is a flow diagram illustrating an exemplary general
method in accordance with the present disclosure
[0011] FIG. 3 is a graph illustrating energy savings as a result of
reductions in pump speeds.
[0012] FIG. 4 is a graph illustrating exemplary means for
determining whether to operate the system of the present disclosure
with 1 pump or 2 pumps.
[0013] FIG. 5 a graph illustrating exemplary means for operating
the system of the present disclosure at the dividing point between
pump speed control for higher flow demand situations and freshwater
shunt valve control for lower flow demand situation.
[0014] FIG. 6 is a flow diagram illustrating an exemplary detailed
method in accordance with the present disclosure.
[0015] FIG. 7 is a flow diagram illustrating a configuration
sub-method of the method shown in FIG. 6.
[0016] FIG. 8 is a flow diagram illustrating an auto operation
sub-method of the method shown in FIG. 6.
[0017] FIG. 9 is a flow diagram illustrating a teach in sub-method
of the method shown in FIG. 6.
[0018] FIG. 10 is a flow diagram illustrating a startup control
sub-method of the method shown in FIG. 6.
[0019] FIG. 11 is a flow diagram illustrating a backup pump &
operation sub-method of the method shown in FIG. 6.
[0020] FIG. 12 is a graph illustrating the startup control
sub-method shown in FIG. 9.
DETAILED DESCRIPTION
[0021] An intelligent sea water cooling system and method in
accordance with the present disclosure will now be described more
fully hereinafter with reference to the accompanying drawings, in
which preferred embodiments of the invention are shown. The
disclosed system and method, however, may be embodied in many
different forms and should not be construed as limited to the
embodiments set forth herein. Rather, these embodiments are
provided so that this disclosure will be thorough and complete, and
will fully convey the scope of the invention to those skilled in
the art. In the drawings, like numbers refer to like elements
throughout.
[0022] Referring to FIG. 1, a schematic representation of an
exemplary intelligent sea water cooling system 10 (hereinafter "the
system 10") is shown. The system 10 may be installed onboard any
type of seafaring vessel or offshore platform having one or more
engines 11 that require cooling. Only a single engine 11 is shown
in FIG. 1, but it will be appreciated by those of ordinary skill in
the art the engine 11 may be representative of a plurality of
engines or various other loads onboard a vessel or platform that
may be coupled to the cooling system 10.
[0023] The system 10 may include a sea water cooling loop 12 and a
fresh water cooling loop 14 that are thermally coupled to one
another by a heat exchanger 15 as further described below. Only a
single heat exchanger 15 is shown in FIG. 1, but it is contemplated
that the system 10 may alternatively include two or more heat
exchangers for providing greater thermal transfer between the sea
water cooling loop 12 and the fresh water cooling loop 14 without
departing from the present disclosure.
[0024] The sea water cooling loop 12 of the system 10 may include a
main pump 16, a secondary pump 18, and a backup pump 20. The pumps
16-20 may be driven by respective variable frequency drives 22, 24,
and 26 (hereinafter "VFDs 22, 24, and 26"). The pumps 16-20 may be
centrifugal pumps, but it is contemplated that the system 10 may
alternatively or additionally include various other types of fluid
pumps.
[0025] The VFDs 22-26 may be operatively connected to respective
main, secondary, and backup controllers 28, 30, and 32 via
communications links 40, 42, and 44. Various sensors and monitoring
devices 35, 37, and 39, including, but not limited to, vibration
sensors, pressure sensors, bearing temperature sensors, and other
possible sensors, may be operatively mounted to the pumps 16, 18
and 20 and connected to the corresponding controllers 28, 30 and 32
via the communications links 34, 36, and 38. These sensors may be
provided for monitoring the health of the pumps 16, 18, and 20 as
further described below.
[0026] The controllers 28-32 may further be connected to one
another by communications link 46. The communication link 46 may be
transparent to other networks, providing supervising communication
capability. The controllers 28-32 may be configured to control the
operation of the VFDs 22-26 (and therefore the operation of the
pumps 16-20) to regulate the flow of sea water to the heat
exchanger 15 as further described below. The controllers 28-32 may
be any suitable types of controllers, including, but not limited
to, proportional-integral-derivative (PID) controllers and/or a
programmable logic controllers (PLCs). The controllers 28-32 may
include respective memory units and processors (not shown) that may
be configured to receive and store data provided by various sensors
in the cooling system 10, to communicate data between controllers
and networks outside of the system 10, and to store and execute
software instructions for performing the method steps of the
present disclosure as described below.
[0027] The communications links 34-46, as well as communications
links 81, 104 and 108 described below, are illustrated as being
hard wired connections. It will be appreciated, however, that the
communications links 34-46, 91, 104 and 108 of the system 10 may be
embodied by any of a variety of wireless or hard-wired connections.
For example, the communication links 34-46, 91, 104 and 108 may be
implemented using Wi-Fi, a Bluetooth, PSTN (Public Switched
Telephone Network), a satellite network system, a cellular network
such as, for example, a GSM (Global System for Mobile
Communications) network for SMS and packet voice communication,
General Packet Radio Service (GPRS) network for packet data and
voice communication, or a wired data network such as, for example,
Ethernet/Internet for TCP/IP, VOIP communication, etc.
[0028] The sea water cooling loop 12 may include various piping and
piping system components ("piping") 50, 52, 54, 56, 58, 60, 62, 64,
66, 68, 70 for drawing water from the sea 72, through the pumps
16-20, and for circulating the sea water through the sea water
cooling loop 12, including a seawater side of the heat exchanger
15, as further described below. The piping 50-70, as well as piping
84, 86, 88, 90, 92, and 94 of the fresh water cooling loop 14
described below, may be any type of rigid or flexible conduits,
pipes, tubes, or ducts that are suitable for conveying water, and
may be arranged in any suitable configuration aboard a vessel or
platform as may be appropriate for a particular application.
[0029] The sea water cooling loop 12 may further include a
discharge valve 89 disposed intermediate the conduits 68 and 70 and
connected to the main controller 28 via communications link 91. The
discharge valve 89 may be adjustably opened and closed to vary the
operational characteristics (e.g., pressure) of the pumps 16-20 as
further described below. In one non-limiting exemplary embodiment,
the discharge valve is a throttle valve.
[0030] The fresh water cooling loop 14 of the system 10 may be a
closed fluid loop that includes a fluid pump 80 and various piping
and components 84, 86, 88, 90, 92, and 94 for continuously pumping
and conveying fresh water through the heat exchanger 15 and the
engine 11 for cooling the engine 11 as further described below. The
fresh water cooling loop 14 may further include a 3-way valve 102
that is connected to the main controller 28 via communications link
104 for controllably allowing a specified quantity of water in the
fresh water cooling loop 14 to bypass the heat exchanger 15 as
further described below.
[0031] A temperature in the fresh water cooling loop 14 may be
measured and monitored by the main controller 28 for facilitating
various control operations of the cooling system 10. Such
temperature measurement may be performed by a resistance
temperature detector 106 (hereinafter "RTD 106") or other
temperature measurement device that is operatively connected to the
fresh water cooling loop 14. The RTD 106 is shown in FIG. 1 as
measuring the temperature of the fresh water cooling loop 14 on the
inlet side of the engine 11, but it is contemplated that the RTD
106 may alternatively or additionally measure the temperature of
the fresh water cooling loop 14 on the outlet side of the engine
11. The RTD 106 may be connected to the main controller 28 by
communications link 108, or, alternatively, may be an integral,
onboard component of the main controller 28.
[0032] Referring to FIG. 2, a flow diagram illustrating a general
exemplary method for operating the system 10 in accordance with the
present disclosure is shown. The method will be described in
conjunction with the schematic representation of the system 10
shown in FIG. 1. Unless otherwise specified, the described method
may be performed wholly or in part by the controllers 28-32, such
as through the execution of various software algorithms by the
processors thereof.
[0033] At step 200, the system 10 may be activated, such as by an
operator making an appropriate selection in an operator interface
(not shown) of the system 10. Upon such activation, the main and
secondary controllers 28 and 30 may command the VFDs 22 and 24 to
begin driving at least one of the pumps 16 and 18. The pumps 16 and
18 may thus begin pumping sea water from the sea 72, through the
piping 52 and 54, through the pumps 16 and 18, through the piping
58-66, through the heat exchanger 15, and finally through the
piping 68 and 70 and back to the sea 72. As the sea water flows
through the heat exchanger 15, it may cool the fresh water in the
fresh water cooling loop 14 that also flows through the heat
exchanger 15. The cooled fresh water thereafter flows through and
cools the engine 11.
[0034] At step 210 of the exemplary method, the main controller 28
may monitor the temperature of the fresh water in the fresh water
cooling loop 14 via the RTD 106. The main controller 28 may thereby
determine whether the fresh water is at a desired temperature for
providing the engine 11 with appropriate cooling, such as by
comparing the monitored temperature to a predefined temperature
range. For example, the desired temperature level of the freshwater
at the discharge of the heat exchanger may be 35 degrees Celsius,
and the range of the temperature may be +/-3 degrees Celsius.
[0035] If the main controller 28 determines at step 210 that the
monitored temperature of the fresh water exceeds, or is about to
exceed, a predefined temperature level, the main controller 28 may,
at step 220 of the exemplary method, increase the speed of the VFD
22 and may issue a command to the secondary controller 30 to
increase the speed of the VFD 24. The corresponding main and/or
secondary pumps 16 and 18 are thereby driven faster, and the flow
of sea water through the sea water cooling loop 12 is increased.
Greater cooling is thereby provided at the heat exchanger 15, and
the temperature in the fresh water cooling loop 14 is resultantly
decreased. The main controller 28 may additionally command the
3-way valve 102 to adjust its position, thereby adjusting the
amount of fresh water in the fresh water cooling loop 14 through
the heat exchanger 15 in order to achieve optimal cooling of the
fresh water.
[0036] Conversely, if the main controller 28 determines at step 210
that the monitored temperature of the fresh water is below, or is
about to fall below, a predefined temperature level, the main
controller 28 may, at step 230 of the exemplary method, decrease
the speed of the VFD 22 and may issue a command to the secondary
controller 30 to decrease the speed of the VFD 24. The
corresponding main and secondary pumps 16 and 18 are thereby driven
more slowly, and the flow of sea water through the sea water
cooling loop 12 is decreased. Less cooling is thereby provided at
the heat exchanger 15 and the temperature in the fresh water
cooling loop 14 is resultantly increased. The main controller 28
may additionally command the 3-way valve 102 to adjust its
position, thereby diverting some or all of the fresh water in the
fresh water cooling loop 14 to bypass the heat exchanger 15 in
order to further reduce the cooling of the fresh water.
[0037] In some embodiments it may be desirable to maintain a
minimum required pressure in the seawater cooling loop 12. (It will
be appreciated that there are cases such minimum pressure
requirements may be dictated by the demands of other connected
systems, such as fire-man, sanitary, or the like.) To achieve such
minimum pressure in the seawater cooling loop 12 the pumps 16, 18
may be required to operate at a speed that is not consistent with
the flow required to meet the fresh water temperature target. In
such a case the main controller 28 at step 240 may set a speed and
activate valve 102 to assume the set temperature control.
[0038] In all cases the centrifugal pump operates at the point in
which the system curve crosses the pump curve. In some embodiments
the hydraulics of the pump within the seawater cooling loop 12 will
not allow the pump or pumps to operate in a stable low pressure
requiem or have the ability to maintain the precision required by
the cooling system solely by speed control. In such case, the
inclusion of a control throttling valve 89 in the seawater
discharge line after the heat exchanger 15 allows extended
operating range. Addition of this valve 89 can change the system
curve, and its position can be adjusted, so as to control the
system curve changing the operating point and extending control to
a lower speed. This adjustment can enable the pumps 16, 18 to be
operated at a lower speed than would normally be the case while
still providing the desired low level of cooling to the fresh water
loop 14. As will be appreciated, this arrangement can extend the
operating range to save additional energy.
[0039] Under other circumstances, such as if the system 10 is
operating in particularly cold waters and/or if the engine 11 is
idling, it may be desirable to reduce the flow of sea water in the
sea water cooling loop 12 to a rate below what may be achieved
through the reduction of the pump speeds while maintaining stable
operation of the pumps 16 and 18. That is, regardless of how little
flow is required in the sea water cooling loop 12, it may be
necessary to run the pumps 16 and 18 at a minimum safe operating
speed to avoid cavitation or damage to the pumps 16 and 18, for
example. If the main controller 28 determines that such a low flow
rate of sea water is desirable, the main controller 28 may, at step
240, decrease the speed of the VFD 22 to drive the main pump 16 at
or near a minimum safe operating speed, may command the secondary
controller to decrease the speed of the VFD 24 to drive the
secondary pump 18 at or near a minimum safe operating speed (or to
shut down), and may further command the discharge valve 89 to
partially close in order to maintain a required minimum system
discharging pressure. By partially closing the discharge valve 89
thusly, the flow rate in the sea water cooling loop 12 may be
restricted/reduced without further reducing the operational speeds
of the pumps 16 and 18, and the minimum required system discharging
pressure can be maintained. The pumps 16 and 18 may thereby be
operated above their minimum safe operating speeds while achieving
a desired low flow rate in the sea water cooling loop 12.
[0040] By continuously monitoring the temperature in the fresh
water cooling loop 14 and adjusting the pump speeds and flow rate
in the sea water cooling loop 12 in the manner described above, the
pumps 16 and 18 may be driven only as fast as is necessary to
provide a requisite amount of cooling at the heat exchanger 15. The
system 10 may therefore be operated much more efficiently and may
provide significant fuel savings relative to traditional sea water
cooling systems in which sea water pumps are driven at a constant
speed regardless of temperature variations. Such improved
efficiency is illustrated in the graph shown in FIG. 3. As will be
appreciated by those of ordinary skill in the art, pump power "P"
is proportional to the cube of pump speed "n," while flowrate "Q"
is proportional to pump speed "n." Thus, when the disclosed system
10 is operated at an optimal flow "Qopt", in lieu of running the
pumps at maximum speed and simply shunting excess flow overboard or
through a recirculation loop, substantial power savings can be
achieved. For example, if Qopt=50% of the maximum seawater flow,
then the pumps 16, 18 need only be operated at 50% of their maximum
speed to provide Qopt. This reduction in speed results in a power
"P" reduction of 87.5%, as compared to prior systems in which the
pumps 16, 18 are operated at a constant maximum speed.
[0041] At step 250 of the exemplary method, the main controller 28
may determine whether the system 10 should be operated in a
2.times.100% mode or a 2-pump mode in order to achieve a desired
efficiency. That is, it may be more efficient in some situations
(e.g., if minimal cooling is required) to drive only one of the
pumps 16 or 18 and not the other. Alternatively, it may be more
efficient and/or necessary to drive both of the pumps 16 and 18 at
a low speed. The main controller 28 may make such a determination
by comparing the operating speeds of the pumps 16 and 18 to
predefined "switch points." "Switch points" may be threshold
operating speed values that are used to determine whether the
system 10 should switch from 2-pump mode to 2.times.100% mode or
vice versa. For example, if the system 10 is operating in 2-pump
mode and both of the pumps 16 and 18 are being driven at less than
a predetermined percentage of their maximum operating speeds, the
main controller 28 may deactivate the secondary pump 18 and run
only the main pump 16. Conversely, if the system 10 is operating in
2.times.100% mode (e.g., running only the main pump 16) and the
main pump 16 is being driven at greater than a predetermined
percentage of its maximum operating speed, the main controller 28
may activate the secondary pump 18.
[0042] As shown in FIG. 4, The switch points (between one and two
pump operation) may be determined based on the actual flow rate"Q"
in the system 10 compared to optimal flow range "Qopt." According
to the exemplary curve, when Q/Qopt exceeds 127% under single pump
operation, the system can switch to two pump operation to operate
most efficiently. Likewise, when Q/Qopt falls below 74% under two
pump operation, the system can switch to single pump operation. At
the same time, the discharging valve is controlled so that the
required minimum system discharging pressure is maintained at all
times.
[0043] At step 260 of the exemplary method, the main, secondary,
and backup controllers 28, 30, and 32 may periodically transmit
data packets to one another, such as via communications link 46.
Such data packets may include information relating to the critical
operational status, or "health," of each of the controllers 28-32
including their respective pumps 16-20 and VFDs 22-26. If it is
determined that one of the controllers 28-32 has ceased to operate
properly, or is trending in a direction that would indicate a near
or far term malfunction, or if its communications link has
malfunctioned or is otherwise inactive, the duties of that
controller may, at step 260 of the exemplary method, be reassigned
to another one of the controllers. For example, if it is determined
that the secondary controller 30 has ceased to operate properly,
the duties of the secondary controller 30 may be reassigned to the
back-up controller 32. Alternatively, if it is determined that the
main controller 28 has ceased to operate properly, the duties of
the main controller 28 may be reassigned to the secondary
controller 30 and the duties of the secondary controller 30 may be
reassigned to the back-up controller 32. The system 10 is thereby
provided with a level of redundancy that allows to the system 10
carry on with normal operation even after the occurrence of
component failures. Of course, it will be appreciated that the
system 10 may be provided with additional controllers, pumps, and
VFDs if additional layers of redundancy are desired. If the ceased
or questionable controller is repaired and/or restored to
operational conditions, and is brought back to the operation, the
information will be broadcast over the communication link to other
controllers, the back-up controller will automatically stop its
operation of its pump, and will be in stand-by mode for providing
future needs for its back-up role.
[0044] At step 270 of the exemplary method, the main controller 28
may execute a "teach in" function, such as automatically during
each startup operation and/or during its startup from restoration
from a previous failure and/or ceased operation, whereby which
initial operating parameters of the system can be automatically set
without requiring user action. The purpose of the "teach in"
function is to determine a pump operating speed necessary for
ensuring that the system operates at or above a minimum pressure
level, such as may be defined by an operator of a vessel.
[0045] Referring to FIG. 5, as part of the "teach in" process, one
or both operating pumps 16, 18 may be started with the discharge
valve 89 open. Pump speed is then gradually increased until a
required minimum system discharging pressure value "Pmin" (Hmin) is
reached. Power "P*" and pump speed "n*" are also measured using the
pump's associated VFD. These values are used to calculate a value
for initial flow "Q*."
[0046] Referring to FIGS. 6-11, a series of flow diagrams
illustrating a more detailed exemplary method for operating the
system 10 in accordance with the present disclosure will be
described. The method will be described in conjunction with the
schematic representation of the system 10 shown in FIG. 1. Unless
otherwise specified, the described method may be performed wholly
or in part by software algorithms, such as may be executed by one
or more of the controllers 28-32.
[0047] At step 300, the system 10 may be powered on, such as by an
operator making an appropriate selection in a user interface (e.g.,
touchscreen) of one of the controllers 28 or 30. For the purposes
of illustration, it will be assumed in the following description of
the detailed method that the operator is interacting with a user
interface of the controller 28. It will be understood, however,
that the operator may instead interact with a user interface of the
controller 30 in a similar manner.
[0048] At step 301, the system 10 may initially enter an automatic
operation mode. At step 302, the system 10 may present an operator
with an option to place the system 10 in a manual operation mode,
to turn the system 10 off, or to maintain the automatic operation
mode. Such an option may be presented to the operator on a display
of the controller 28. If the operator selects the off option, the
controller 28 may set a VFD operation mode flag to OFF at step 303.
The other controllers 30 and 32 may thereby identify that the
controller 28 is turned off, and the back-up controller 32 may
automatically start-up for joining the operation. If the operator
selects the manual operation mode, the controller 28 may set the
VFD operation mode flag to MANUAL at step 304. This may cause the
VFD 22 to operate the pump at a constant, predefined speed (e.g.,
the rated speed of the VFD 22). The manual mode may thus provide a
back-up function, such as may be necessary if one or more of the
controllers 28-32 malfunctions and/or automatic system operation is
impaired. If the operator selects the automatic operation mode, the
controller 28 may set the VFD operation mode flag to AUTOMATIC at
step 305.
[0049] At step 306 of the exemplary method, the system 10 may
determine whether to operate in a 2.times.100% mode or a 2-pump
mode (as described above in relation to FIG. 4). Such a
determination may be made by comparing the operating speeds of the
pumps 16 and 18 to predefined "switch points." "Switch points" may
be threshold operating speed values that are used to determine
whether the system 10 should switch from 2-pump mode to
2.times.100% mode or vice versa. For example, if the system 10 is
operating in 2-pump mode and both of the pumps 16 and 18 are being
driven at less than 74% of their maximum operating speeds, it may
be determined that the system 10 should switch to 2.times.100%.
Conversely, if the system 10 is operating in 2.times.100% mode
(e.g., running only the main pump 16) and the main pump 16 is being
driven at greater than 127% of its maximum operating speed, it may
be determined that the system 10 should switch to 2-pump mode. The
switch points may be calculated based on known flow rates in the
system 10 as illustrated in FIG. 4.
[0050] If it was determined in step 306 that the system 10 should
operate in 2.times.100% mode, the controller 28 may set a pump flag
to "1" at step 307. Conversely, if it was determined in step 306
that the system 10 should operate in 2-pump mode, the controller 28
may set the pump flag to "2" at step 308.
[0051] At step 309, the controller 28 may present the operator with
an option to perform a configuration of the system 10. If the
operator indicates that he wishes to perform configuration, such as
by making an appropriate selection in the user interface of the
controller 28, the controller may, at step 310, perform the
configuration sub-method shown in FIG. 7. Particularly, the
controller 28 may, at step 310a of the method, check the previously
set pump flag (see step 306 in FIG. 6) to determine whether the
system is operating in 2.times.100% mode or 2-pump mode. If the
system 10 is operating in 2.times.100% mode, the controller 28 may,
at step 310b of the method, designate itself as the main controller
in the system 10 and the controller 30 may be assigned as a back-up
controller. Alternatively, if the system 10 is operating in 2-pump
mode, the controller 28 may, at steps 310c and 310d of the method,
present the operator with an option to designate the controller 28
as either the main controller or the secondary controller of the
system 10.
[0052] If the operator chooses to designate the controller 28 as
the secondary controller in the system 10, the controller 28 may,
at step 310e, designate the other controller 30 as the main
controller in the system 10. Alternatively, if the operator chooses
to designate the controller 28 as the main controller in the system
10, the controller 28 may, at step 310f, designate the other
controller 30 as the secondary controller in the system 10. The
third controller 32 will automatically be assigned as a back-up
controller.
[0053] At step 310g of the method, the controller 28 may establish
a plurality of pump parameters, such as may be provided by a pump
manufacturer. Such pump parameters may include a reference speed
Nref, a reference efficiency Eff for Q/Qopt in a range from
0%-140%, a reference flow Q for Q/Qopt in a range from 0%-140%, a
reference head H for Q/Qopt in a range from 0%-140%, a reference
pressure P for Q/Qopt in a range from 0%-140%, speed limits,
suction pressure limits, discharge pressure limits, bearing
temperature limits, and vibration limits.
[0054] At step 310h of the method, the controller 28 may establish
a plurality of system parameters, such as may be provided by a
vessel operator. Such parameters may include a fresh water
temperature range, a VFD motor speed range, a minimum pressure
level, a fresh water flow, a water heat capacity coefficient, a
heat exchanger surface area, a heat transfer coefficient, presence
of a 3-way valve, and ambient temperature limits.
[0055] At step 310i of the method, the established pump parameters
and system parameters described above may be copied to the other
controller 30 (i.e., if the system 10 is operating in 2-pump mode),
such as by transmission through the communications link 46.
[0056] Returning to FIG. 6, after performing the above-described
configuration sub-method, or if the operator chose not to perform
configuration of the system 10 in step 309, the controller 28 may,
at step 311 of the method, determine whether the system 10 is
running under automation operation (described above). If the
controller 28 determines that the system 10 is currently running
under automatic operation, the controller may, at step 312, perform
the auto operation and control sub-method shown in FIG. 8.
Particularly, the controller 28 may, at step 312a, calculate a
target flow rate QT for the flow of sea water in the sea water
cooling loop 12. For example, QT may be calculated as the result of
PI controller, PI(Ttarget-TFW), wherein Ttarget is a desired
temperature level of the fresh water in the fresh water cooling
loop 14 and TFW is the actual temperature of the fresh water in the
fresh water cooling loop 14 as measured, for example, by RTD
106.
[0057] At step 312b of the method, the controller may determine
whether the target flow rate QT is greater than the actual flow
rate Q* in the sea water cooling loop 12. If it is determined that
QT is greater than Q*, the controller 28 may, at step 312c, operate
the 3-way valve 102 to assume a fully closed position (i.e., all
freshwater flows through the heat exchanger 15). At step 312e, the
controller 28 may adjust the speeds of the pumps 16 and 18 (or only
the pump 16 if the system 10 is in 2.times.100% mode) at a desired
speed "n" according to the equation n=n*QT/Q*, where n* is the
minimum speed level at which the required minimum system
discharging pressure (described above) is obtained.
[0058] Alternatively, if it is determined in step 312b that QT is
less than Q*, the controller 28 may, at step 312d, operate the
3-way valve 102 to assume a partially open position to cause a
certain amount of freshwater to bypass the heat exchanger 15. At
step 312f, the controller 28 may further calculate an amount which
the 3-way shunt valve 102 should be opened, such as may be given by
the result of PI controller, PI(Ttarget-TFW), and may command the
3-way shunt 102 valve to open by such an amount. The controller 28
may further maintain the minimum speed n* of the pumps 16 and 18
(or only the pump 16 if the system 10 is in 2.times.100% mode).
[0059] If the controller 28 previously stopped the system 10 at
step 311, the controller 28 may, at step 313 of the method,
determine whether the system is in AUTO mode (described above). If
so, the controller 28 may perform a startup process, the first step
of which is to execute, at step 314, the "teach in" sub-method
shown in FIG. 9. Particularly, the controller may, at step 314a of
the method, increase the speeds of the pumps 16 and 18 (or only the
pump 16 if the system 10 is in 2.times.100% mode) until a required
minimum system discharging pressure level Pmin is reached in the
sea water cooling loop 12. After Pmin is reached, the controller 28
may, at step 314b of the method, read a "teach in" speed n* and a
teach in pressure P* from the VFDs 22 and 24 (or only the VFD 22 if
the system 10 is in 2.times.100% mode), calculate a teach in flow
Q* and a new minimum pressure level Pmin, and may store Q*, P*, n*,
and Pmin. Q* can be calculated by using pump head-and-flow curve,
which the pump manufacturer can provide.
[0060] After performing the "teach in" sub-method, the controller
28 may, at step 315 of the method, perform the "startup control"
sub-method shown in FIG. 10. Particularly, the controller 28 may,
at step 315a, increase the speeds of the pumps 16 and 18 (or only
the pump 16 if the system 10 is in 2.times.100% mode) to the
teach-in speed level n* (also the minimum speed for the system
generates the required minimum system discharging pressure). The
controller 28 may then proceed to perform the auto operation
sub-method of step 312 described above in relation to FIG. 8.
[0061] A after performing the above-described "auto operation"
sub-method or "startup control" sub-method, or if run was not
clicked in step 313, the controller 28 may, at step 316, determine
whether there are any alarms in the system 10 (e.g., with
predefined time delays to ensure that the alarms are not false
alarms produced by transient electrical "noise"). For example, the
controller 28 may determine whether either of the pumps 16 or 18
(or only the pump 16 if the system 10 is in 2.times.100% mode) is
operating outside of the pump parameters established in the
configuration sub-method described above, such as may be determined
from the sensors 35, 37, and 39.
[0062] If the controller 28 determines that either of the pumps 16
or 18 is operating outside of their established parameters, the
controller 28 may, at step 317 of the method (FIG. 6), determine
whether the backup pump 20 is ready for operation. If it is
determined that the backup pump 20 is ready for operation, the
controller 28 may, at step 318, perform the backup pump &
operation sub-method shown in FIG. 11. Particularly, the controller
28 may, at step 318a, command the controller 32 of the backup pump
20 to increase the speed of the backup pump 20 to the same speed
level of the VFD 22. Finally, the controller 28 may, at step 319 of
the method, stop operation of the faulty pump 16 or 18 if such
operation had not ceased previously.
[0063] After step 319, or if the controller 28 determined that
there were no alarms in step 316 or that the backup pump 20 was not
ready in step 317, the controller may, at step 320 of the method,
use the sensors 35, 37, and 39 to measure a sea water temperature
TSW, an ambient temperature Tamb, a fresh water temperature TFW, a
pump vibration V, a pump suction pressure PS, a pump discharge
pressure PD, and a pump bearing temperature T. At step 321 of the
method, the controller 28 may read from the VFDs 22 and 24 (or only
the VFD 22 if the system 10 is in 2.times.100% mode) an actual
speed nACT, a power consumption P or torque or current and
voltage.
[0064] At step 322, the controller 28 may display any warnings
related to operation of the pumps 16 and 18 or the system 10, and
the entire method described above may be repeated starting at step
301. As used herein, an element or step recited in the singular and
proceeded with the word "a" or "an" should be understood as not
excluding plural elements or steps, unless such exclusion is
explicitly recited. Furthermore, references to "one embodiment" of
the present invention are not intended to be interpreted as
excluding the existence of additional embodiments that also
incorporate the recited features.
[0065] While certain embodiments of the disclosure have been
described herein, it is not intended that the disclosure be limited
thereto, as it is intended that the disclosure be as broad in scope
as the art will allow and that the specification be read likewise.
Therefore, the above description should not be construed as
limiting, but merely as exemplifications of particular embodiments.
Those skilled in the art will envision other modifications within
the scope and spirit of the claims appended hereto.
[0066] The various embodiments or components described above may be
implemented as part of one or more computer systems. Such a
computer system may include a computer, an input device, a display
unit and an interface, for example, for accessing the Internet. The
computer may include a microprocessor. The microprocessor may be
connected to a communication bus. The computer may also include
memories. The memories may include Random Access Memory (RAM) and
Read Only Memory (ROM). The computer system further may include a
storage device, which may be a hard disk drive or a removable
storage drive such as a floppy disk drive, optical disk drive, and
the like. The storage device may also be other similar means for
loading computer programs or other instructions into the computer
system.
[0067] As used herein, the term "computer" may include any
processor-based or microprocessor-based system including systems
using microcontrollers, reduced instruction set circuits (RISCs),
application specific integrated circuits (ASICs), logic circuits,
and any other circuit or processor capable of executing the
functions described herein. The above examples are exemplary only,
and are thus not intended to limit in any way the definition and/or
meaning of the term "computer."
[0068] The computer system executes a set of instructions that are
stored in one or more storage elements, in order to process input
data. The storage elements may also store data or other information
as desired or needed. The storage element may be in the form of an
information source or a physical memory element within the
processing machine.
[0069] The set of instructions may include various commands that
instruct the computer as a processing machine to perform specific
operations such as the methods and processes of the various
embodiments of the invention. The set of instructions may be in the
form of a software program. The software may be in various forms
such as system software or application software. Further, the
software may be in the form of a collection of separate programs, a
program module within a larger program or a portion of a program
module. The software also may include modular programming in the
form of object-oriented programming. The processing of input data
by the processing machine may be in response to user commands, or
in response to results of previous processing, or in response to a
request made by another processing machine.
[0070] As used herein, the term "software" includes any computer
program stored in memory for execution by a computer, such memory
including RAM memory, ROM memory, EPROM memory, EEPROM memory, and
non-volatile RAM (NVRAM) memory. The above memory types are
exemplary only, and are thus not limiting as to the types of memory
usable for storage of a computer program.
* * * * *